1. Field of the Invention
The present invention relates to a paper-feeding roller for use in a paper-feeding mechanism of a copying machine, a printer, a facsimile apparatus, and the like. More particularly, in the paper-feeding roller of the present invention, an annular elastic member (rubber roll) mounted on the peripheral surface of a core has a three-layer construction composed of an inner layer, an intermediate layer, and an outer layer. The hardness of each of the three layers is preferably set to suppress a drop of the coefficient of friction of the paper-feeding roller and generation of a chattering phenomenon.
2. Description of the Related Art
Various types of paper-feeding rollers are used for paper-feeding mechanisms of an electrostatic copying machine, various types of printers, a facsimile apparatus, an automatic teller machine (ATM), and the like. The paper-feeding roller means a roller that transports paper owing to friction between the surface thereof and paper, with the paper-feeding roller rotating in contact with the paper. The paper-feeding roller includes a paper-supplying roller, a resist roller, a transfer roller, and the like.
As the material for the rubber roll of the paper-feeding roller, natural rubber, urethane rubber, ethylene-propylene-diene rubber (EPDM) rubber, polynorbornane rubber, silicone rubber, chlorinated polyethylene rubber, and the like have been hitherto used.
Many rubber rolls composing the paper-feeding roller have a one-layer construction consisting of a non-foamed layer. The coefficient of friction of the rubber roll having the one-layer construction is liable to drop, when a large number of paper is supplied thereto. As a result, the rubber roll deteriorates in its paper-feeding performance. Thereby defective paper-feeding occurs or a chattering phenomenon is generated owing to sliding of paper on the surface of the rubber roll. In recent years, there are proposed rubber rolls having a two-layer construction or a three-layer construction to improve the wear resistance thereof and suppress a drop of the coefficient of friction thereof.
For example, disclosed in Japanese Patent Application Laid-Open No. 2001-341862 (patent document 1) is the rubber roll having the two-layer construction composed of the foamed inner layer and the non-foamed outer layer. Also disclosed in the patent document 1 is the rubber roll having the three-layer construction composed of the non-foamed inner layer, the foamed intermediate layer, and the non-foamed outer layer.
In the patent document 1, to allow the rubber roll to have a preferable coefficient of friction and nip amount, the ASKA-C hardness of the foamed layer is adjusted to not more than 50 degrees, and the JIS-A hardness of the non-foamed layer is adjusted to not more than 60 degrees. The inner layer of the rubber roll having the three-layer construction is provided to fix the rubber roll to the core strongly.
Disclosed in Japanese Patent Application Laid-Open No. 2002-48130 (patent document 2) is the rubber roll having the three-layer construction composed of the base rubber layer (inner layer) that is considered to be non-foamed layer and the comparatively thin intermediate and outer layers those are considered to be a non-foamed layer respectively formed on the peripheral surface of the base rubber layer. Proposed in the patent document 2 is the composition of the base rubber layer effective for improving fatigue resistance of the rubber roll and suppressing bleeding of components, but the hardness of the intermediate layer and that of the outer layer are not specified.
The rubber roll having the two-layer construction composed of the inner layer and the outer layer is disclosed in Japanese Patent Application Laid-Open No. 2002-347972 (patent document 3). The JIS-A hardness of the inner layer and that of the outer layer are adjusted to a specific range respectively. To improve the wear resistance of the outer layer and reduce the generation of the chattering phenomenon, the JIS-A hardness of the outer layer and that of the inner layer are adjusted to the range of 35 to 50 degrees and not more than 25 degrees respectively.
Patent document 1: Japanese Patent Application Laid-Open No. 2002-341862
Patent document 2: Japanese Patent Application Laid-Open No. 2002-48130
Patent document 3: Japanese Patent Application Laid-Open No. 2002-347972